Removal of Inorganics

Chemical addition for the removal of inorganic compounds is a well-established technology. There are three common types of chemical addition systems that depend upon the low solubility of inorganics at a specific pH. These include the carbonate system, the hydroxide system, and the sulfide system. 

In reviewing the basic solubility products for these systems, the sulfide system removes the most inorganics, with the exception of arsenic, because of the low solubility of sulfide compounds. This increased removal capability is offset by the difficulty in handling the chemicals and the fact that sulfide sludges are susceptible to oxidation to sulfate when exposed to air, resulting in resolubilization of the metals. The carbonate system is a method that relies on the use of soda ash (sodium carbonate) and pH adjustment between 8.2 and 8.5. The carbonate system, although 

Chemical precipitation can be accomplished by either batch- or continuous-flow operations. If the flow is less than 30,000 gpd (21 gpm), a batch treatment system may be the most economical. In the batch system, two tanks are provided, each with a capacity of 1 day s flow. One tank undergoes treatment while the other tank is being filled. When the daily flow exceeds 30,000 gpd, batch treatment is usually not feasible because of the large tankage required. Continuous treatment may require a tank for acidification and reduction, then a mixing tank for chemical addition, and a settling tank. 

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The exchange resins 6nd application in (i) the purification of water (cation-exchange resin to remove salts, followed by anion-exchange resin to remove free mineral acids and carbonic acid), (ii) removal of inorganic impurities from organic substances, (iii) in the partial separation of amino acids, and (iv) as catalysts in organic reactions (e.g., esterification. Section 111,102, and cyanoethylation. Section VI,22). 

The technology is primarily applicable to the removal of inorganic fumes, vapors, and gases (e.g., chromic acid, hydrogen sulfide, ammonia, chlorides, fluorides, and SOj) volatile organic compounds (VOC) and particulate matter (PM), including PM less than or equal to 10 micrometers ( m) in aerodynamic diameter (PM,q), PM less than or equal to 2.5 m in aerodynamic diameter (PMj 5), and hazardous air pollutants (HAP) in particulate form (PM ap)-... 

The primary target of studies on photocatalytic semiconductor suspensions has been water cleavage by visible light. Suspension-based photocatalytic processes are also useful for the removal of inorganic (metal ions) and organic pollutants, the reduction of CO2, the photodestruction of bacteria and viruses, and various organic reactions an example is the use of Pt-loaded CdS for the photocatalytic racemization of L-lysine [210]. 

The removal of inorganic salts from reaction mixtures afforded by polymeric materials may be simply and effectively accomplished by dialysis,166 178 after decomposition of remaining periodate with ethylene glycol130 131 or butylene glycol. 161 170 Alternatively, the iodate and periodate ions may be removed as such, or after reduction to free iodine. The iodate and periodate ions have been effectively precipitated by means of sodium carbonate plus manganous sulfate,6 or by lead dithionate,191 barium chloride,24 192 193 strontium hydroxide194 202 or barium hydroxide,203 204 lead... 

Removal of inorganic interferences, particularly the removal of bromide interference in seawater by fivefold dilution of the sample, the removal of nitrate by addition of sulfamic acid, and the removal of metals by passage through Amberlite IR 120 cation exchange resin. 

Even if removal of inorganic carbon is complete, the analysis of the remaining carbon is difficult. At a concentration of 1 ppm, a normal value for surface water in the open ocean, a 1 ml sample will contain 1 ig carbon. If we are interested in differences between samples, we must strive for a precision of 5% or 0.05 xg C per ml sample. This requirement places severe constraints on the sensitivity and precision of instrumentation. 

The determination of dissolved organic carbon by oxidation methods in water comprises three analytical steps the removal of inorganic carbon from the sample, oxidation of the organic compounds to carbon dioxide, and the quantitative determination of the resulting carbon dioxide. The methods of oxidation can be classified into three major groups ... 

Hannaker and Buchanan [82] used a method based on wet oxidation with potassium persulfate [83] for the determination of dissolved organic content in concentrated brines following the removal of inorganic carbonates with phosphoric acid. The method involves wet oxidation with potassium persulfate at 130 °C followed by a hot copper oxidation and gravimetric measurement of the carbon dioxide produced. The technique overcomes difficulties of calibration curvature, catalytic clogging, and instrument fouling often encountered with instrumental methods. 

A pH of 3 was optimal for the complete removal of inorganic carbon and the most efficient oxidation of nitrogen-free organic compounds, while a pH of 2.5 was optimal for nitrogenous compounds (Fig. 11.1). 

Gershey et al. [58] have pointed out that persulfate and photo-oxidation procedures will determine only that portion of the volatile organics not lost during the removal of inorganic carbonate [30,79,92,181]. Loss of the volatile fraction may be reduced by use of a modified decarbonation procedure such as one based on diffusion [98]. Dry combustion techniques that use freeze-drying or evaporation will result in the complete loss of the volatile fraction [72,79, 92,93],... 

Maeda, S., S. Nakashima, T. Takeshita, and S. Higashi. 1985. Bioaccumulation of arsenic by freshwater algae and the application to the removal of inorganic arsenic from an aqueous phase, n. By Chlorella vulgaris isolated from arsenic-polluted environment. Separation Sci. Technol. 20 153-161. 

Mechanical and biological methods are very effective on a large scale, and physical and chemical methods are used to overcome particular difficulties such as final sterilization, odor removal, removal of inorganic and organic chemicals and breaking oil or fat emulsions. Normally, no electrochemical processes are used [10]. On the other hand, there are particular water and effluent treatment problems where electrochemical solutions are advantageous. Indeed, electrochemistry can be a very attractive idea. It is uniquely clean because (1) electrolysis (reduction/oxidation) takes place via an inert electrode and (2) it uses a mass-free reagent so no additional chemicals are added, which would create secondary streams, which would as it is often the case with conventional procedures, need further treatment, cf. Scheme 10. 

Normally, treatment of coproduced groundwater during hydrocarbon recovery operations will include, as a minimum, oil-water separation and the removal of dissolved volatile hydrocarbon fractions (i.e., benzene, toluene, and total xylenes). In addition, removal of inorganic compounds and heavy metals (i.e., iron) is often required. Dissolved iron, a common dissolved constituent in groundwater, for example, may require treatment prior to downstream treatment processes to prevent fouling problems in air-stripping systems. Heavy metals removal is normally accomplished by chemical precipitation. 

Chemical precipitation has traditionally been a popular technique for the removal of heavy metals and other inorganics from wastewater streams. However, a wide variety of other techniques also exist. For example, ion-exchange, reverse osmosis, evaporation, freeze crystallization, electrodialysis, cementation, catalysis, distillation, and activated carbon have all been used for removal of inorganics. 

The waste from this treatment scheme should be suitable for discharge or reuse with a possible need for removal of inorganic dissolved solids if a "zero discharge" system is used. 

Dousova et al. [142] found that calcined Mg/Al LDHs were effective in removal of As (V) compounds from aqueous solutions at 293 K and neutral pH utilizing the memory effect . More than 70 % of As (V) compoimds were removed from aqueous solution at low sorbent-solution ratios. Parida et al. also studied the affinity of Mg/Fe LDHs toward the removal of inorganic selenite (SeOs ) from aqueous media [143]. The results indicated that the efficacy of SeOs removal increases with a decrease in either pH or temperature. 

Offers potential applications in the removal of inorganic constituents, such as heavy metals, that conventional soil washing technology lacks. 

The sulfinyl chloride thus obtained is satisfactory for further preparative work. The checkers found that the average yield of crude material after removal of inorganic salts by filtration was about 81%. 

The first approach relies heavily on coal pretreatment. Although such pretreatment may be possible, the complete removal of inorganic minerals does not appear practical. 

Post Treatment - oxidation of organic compounds in the hydrolysate through supercritical water oxidation (SCWO) and removal of inorganic salts through evaporation... 

Nakajima, T., Xu, Y.-H., Mori, Y. et al. (2005) Combined use of photocatalyst and adsorbent for the removal of inorganic arsenic(III) and organoarsenic compounds from aqueous media. Journal of Hazardous Materials, 120(1-3), 75-80. 

X-ray crystallographic analysis of the orange single crystals, which were obtained after the removal of inorganic salts and naphthalene, has revealed that the structure of the orange crystal is that of the digermene ( )-Tbt(Mes)Ge=Ge(Mes)Tbt 10, the dimer of the germylene Tbt(Mes)Ge 2225. The details of the structural analysis of 10 will be discussed later. 

The chelator, 2,3-dimercapto-1 -propanesuifonic acid (DMPS) binds with metals via a sulfate and two sulhydryl groups. It is used for the removal of inorganic and methyl mercury and may reduce the toxicides of cQpper, nickel, and cadmium (Zuiderveen, 1994). 

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